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Brain fault 'may be linked to ADHD'

Attention-deficit/hyperactivity disorder (ADHD) may be linked to a faulty “off-switch” in the brain, a new study has found.

Researchers from the University of Nottingham have suggested that children with ADHD require either much greater incentives or medication (methylphenidate, often known as Ritalin) to focus on a task.

Scientists carried out brain scans on 18 children with ADHD aged between nine and 15 in an effort to discover why they had difficulty concentrating. Their brains were compared with those of 18 similar children without ADHD.

If the incentive to carry out a task was low, then those with ADHD failed to “switch off” brain regions involved in mind-wandering.

But when stronger incentives were given, or when youngsters took their medication, their brain activity was the same as for children without ADHD, according to researchers.

All the children played a computer game that involved hitting green aliens as quickly as possible while avoiding black ones.

The reward for avoiding black aliens was then increased to study the effect of incentives.

Professor Chris Hollis, who led the study, said: “The results are exciting because for the first time we are beginning to understand how, in children with ADHD, incentives and stimulant medication work in a similar way to alter patterns of brain activity and enable them to concentrate and focus better.

“It also explains why in children with ADHD their performance is often so variable and inconsistent, depending as it does on their interest in a particular task.”

The study, which was funded by the Wellcome Trust, has been published in the Journal of Child Psychology and Psychiatry.